Field-Free Spin–Orbit Torque Switching Enabled by the Interlayer Dzyaloshinskii–Moriya Interaction

Perpendicularly magnetized structures that are switchable
using
a spin current under field-free conditions can potentially be applied
in spin–orbit torque magnetic random-access memory (SOT-MRAM).
Several structures have been developed; however, new structures with
a simple stack structure and MRAM compatibility are urgently needed.
Herein, a typical structure in a perpendicular spin-transfer torque
MRAM, the Pt/Co multilayer and its synthetic antiferromagnetic counterpart
with perpendicular magnetic anisotropy, was observed to possess an
intrinsic interlayer chiral interaction between neighboring magnetic
layers, namely, the interlayer Dzyaloshinskii–Moriya interaction
(DMI) effect. Furthermore, using a current parallel to the eigenvector
of the interlayer DMI, we switched the perpendicular magnetization
of both structures without a magnetic field, owing to the additional
symmetry breaking introduced by the interlayer DMI. This SOT switching
scheme realized in the Pt/Co multilayer and its synthetic antiferromagnet
structure may open a new avenue toward practical perpendicular SOT-MRAM
and other SOT devices.